Copending application Ser. No. 582,305, filed Sep. 14, 1990, entitled "Multiresolution Digital Imagery Photofinishing System", by S. Kristy, assigned to the assignee of the present application and the disclosure of which is herein incorporated, describes a digital image processing system wherein photographic still images, such as those captured by way of a 35 mm camera, are digitized and recorded on an optical compact disc (CD), for subsequent playback on a CD player. Image data files are created by scanning the images on a roll of developed photographic film to produce digitized pixel data for the images, and storing the pixel data as image data files. A relatively permanent digital storage medium, such as an optical disc readable by a laser pickup, is then produced. A user having such a disc loads the disc into a disc player coupled to a display unit such as a video monitor or television. Then, by entering suitable commands into the disc player or a separate control unit, such as an IR remote (hand-held) device, the user displays selected images on the display unit.
A low cost, reduced complexity frame store/data retrieval architecture, incorporated into a CD player and which provides for rapid call-up of images stored as digitized image data and display of the images on a consumer television color monitor, is described in a copending U.S. patent application Ser. No. 583,265, filed Sep. 14, 1990, entitled "Mechanism for Controlling Presentation of Displayed Image", by K. Parulski et al, assigned to the assignee of the present application, and the disclosure of which being herein incorporated.
As described in the above-referenced applications, each captured image is digitized by the scanner and stored `as is`, regardless of its orientation on the film. Annexed to each image file is a header file which contains orientation, aspect ratio and other minilab operator-generated information that is readable by the data retrieval microcontroller of a CD player, to control the coupling of the image data to a reproduction device (e.g. TV display). Images are displayed by providing image data residing in an image memory to an output of the apparatus at which a display device is to be coupled. The apparatus maps image data pixels to pixels of a display screen of the display device for correct orientation and aspect ratio.
Now, although the above-referenced photo compact disc schemes provide a number of photographic image processing and playback capabilities not heretofore available, it would be desirable to provide additional convenience and flexibility to the user. First, there is inevitably a certain latency time between the time the user enters a command by way of an I/O device (e.g. keyboard, IR remote control unit) to view a selected image, and the time that image actually appears on the display screen. This latency time is largely due to the time required for locating the image data file on disc, reading the image data from the disc, and then loading the read-out image data into the image memory or frame store in the CD player. Typically, this latency time is about 1 to 4 seconds, long enough to be noticeable and inconvenient to the user. It would be desirable to reduce this latency time to a time short enough not to be noticeable to the user.
Secondly, some user applications of image display systems involve displaying multiple images, for instance for side-by-side comparison. Medical imaging applications and slide presentations are two applications in which display of two or more images in a side-by-side format is useful. Also, consumers may want to compare images side-by-side, for instance to select a preferred one of several portrait photos of the same person. In addition, the user may wish to browse through a library of images stored on the CD and select plural images for display.
One possible mechanism for displaying multiple images involves redundant playback and display. Unfortunately, the constant complexity of such a scheme would be prohibitive for a consumer or for other users who have budgetary or equipment space limitations. A user of a system which does not support multiple images has to switch back and forth between the images to be displayed and compared, and must repeatedly enter a display command for the images to be played back. The fact that such playback/display commands must be repeatedly entered and that the images are not simultaneously on display are inconvenient to the user. Accordingly, it would be desirable to save the user the inconvenience of entering repeated commands by allowing for simultaneous display of multiple images.